This invention relates to a method of forming a ply member, particularly a carcass ply for a radial tire.
A method of forming ply members of this kind hitherto used was disclosed in Japanese Patent Application Laid-open No. 49-76,978. In this disclosed method, after the outer circumferential length of a forming drum is divided into n sections of equal circumferential lengths, n pieces of belt-shaped members are progressively attached to the respective divided sections of the outer circumference of the forming drum so that the belt-shaped members extend in parallel with the axis of the forming drum to form a carcass ply.
In this method of the prior art, however, when sizes of tires or diameters of forming drums are changed, it is required to change widths of belt-shaped members. Therefore, belt-shaped members having widths compatible with the diameters of forming drums must be prepared for forming drums to be used. In other words, every time the diameter of the forming drum is changed, different belt-shaped members must be supplied to a feeder so that processes for forming ply members are considerably increased and spaces for storing a lot of kinds of belt-shaped members are also increased.
In this method of the prior art, moreover, a plurality of belt-shaped members are attached on the outer circumferential surface of a forming drum in overlapping or abutting state. With the former state, the overlapping portions of formed ply members are higher than the remaining portions so that tires produced from such ply members including the overlapping portions are poor in uniformity. With the latter state, there are mixed with overlapping portions and not joined portions at the abutting edges of the belt-shaped members attached around the forming drum in connection with extending directions of embedded reinforcing cords. Consequently, the quality of joined portions does not fulfill the usual requirement and the uniformity of produced tires becomes insufficient.